To date, there are no biomarkers in spondyloarthritis that can differentiate between spondyloarthritis and fibromyalgia or other pathologies. Fecal calprotectin is a biomarker that is increasingly used in inflammatory diseases of the digestive tract. A growing interest in this biomarker is emerging in rheumatology, several publications have focused on its interest in rheumatoid arthritis, highlighting an association between serum calprotectin levels and disease activity. In spondyloarthritis, a few studies seem to show that it could be a marker of disease activity. Although a 2012 study found no difference in serum calprotectin levels between subjects with spondyloarthritis and controls. Still others have shown that it could be a predictive factor of radiological evolution in the same disease key. These data support, despite the questionable results of the Klingberg study, the value of this dosage in spondyloarthritis. The objective of this work is to show that this assay could be useful to differentiate spondyloarthritis from other pathologies with similar clinical presentation such as fibromyalgia. Difficulties classically encountered in common practice in rheumatology

Inclusion Criteria:

Patients in the active line of the rheumatology department with one of the following criteria:

active spondyloarthritis (BASDAI >4), or spondyloarthritis in low activity (BASDAI<4), or fibromyalgia without associated inflammatory rheumatism, or healthy subjects (without inflammatory rheumatism and without fibromyalgia. Patients who have not objected to the use of their samples

Exclusion Criteria:

Minor patient Subject not affiliated to the social security system Subject deprived of liberty Patient under guardianship or curatorship

Primary clinic care, rheumatology patients at the CHU de NICE